The invention relates to wireless office systems, especially to routing packet data connections in an office system.
Information systems in offices are traditionally designed in such a manner that the telephone network and the data network connecting computers and their peripherals, typically a local area network, are separate networks. The development and convergence of different data networks and telephone networks on one hand and the costs that arise from building and maintaining two parallel networks on the other hand, have led to developing systems for providing the services of telephone networks through local area networks. One significant factor in this development has been an improved applicability of IP (Internet protocol) technology, used conventionally in data networks, to providing telephone services.
In a modern office information system, a mobile system can also be combined to operate through a local area network, in which case voice calls based on a mobile system protocol are routed by means of a local area network (LAN), which typically uses IP technology, through an office-specific base transceiver station (BTS), for instance, to mobile stations (MS). A conventional private branch exchange (PBX) of the office can then be bypassed, and it is also possible to ensure broadband connections at short distances and an excellent quality of speech even in wireless data transmission. Mobile stations establish a wireless connection to an office-specific base transceiver station and then through a local area network both to other mobile stations in the office and through a mobile switching centre (MSC) to external terminals, such as mobile stations outside the office system or terminals of a public switched telephone network (PSTN). One such system is described in patent application U.S. Pat. No. 5,949,775.
A problem with the arrangement described above is that the office system is arranged to route only circuit-switched speech connections to or from the mobile station. Mobile stations establish a connection to the office system through a typical mobile system base transceiver station BTS which comprises an interface which is arranged to route only circuit-switched speech connections to the office system, such as an interface corresponding to the functions of an Abis interface of the GSM system. Packet-switched applications have, however, also been developed for mobile systems. For instance, ETSI (European Telecommunications Standards Institute) has during the last few years drafted GSM 2+ phase standards for the European digital GSM (Global System for Mobile communication) mobile network, which also define a new packet-switched data transmission service GPRS (General Packet Radio Service). GPRS is a packet radio network which utilises the GSM network and endeavours to optimise data packet transmission on the air interface between a mobile station and the GPRS network by means of GPRS protocol layers. A mobile station connected to an office system through an office-specific base transceiver station cannot utilise services implemented by GPRS, because the typical office-specific base transceiver station BTS described above does not comprise an interface to the GPRS system and thus does not support GPRS protocol layers. This restricts the utilisation of different data services on both internal and external mobile connections of an office.